Sounds similar to what Huawei/Altera are doing and what I expect other comms and server OEMs will try out over the next year or so.
http://www.eetimes.com/electronics-news/4401446/Huawei--Altera-mix-FPGA--memory-in-2-5-D-device

Haswell is going to be a 2.5 d module with the Level 4 cache chip next to the processor, the chips connected by fine-pitch high-density thin film interconnects on the Si substrate of the module. Will have lots of interconnects, enabling lots of parallelism in memory accesss by multi - core in CPU / SoC. BTW won't be able to stack chips ( true 3D ) because need to take heat out of the 10 watt CPU.

stacking memory on the CPU makes a lot of sense for any lower-power chip - after all, it's pretty routine in phones. stacking not only gives a performance boost, but saves some power. probably hard to do with a bigger/hotter chip, though.
10W is certainly workable for a tablet, as long as it can race to sleep, low leakage, etc.
I just wish AMD would grow some balls and produce, for instance, an APU with stacked dram so you could tile a bunch of them onto a board. whatever happened to the idea of scalable multiprocessor systems anyway? (with builtin scalable GPU for free!)

It's still a little rumor-like to me. I also saw Anand report it as embedded DRAM as if on-chip, but if it is off- chip, would they use TSV for the speed? Isn't the normal course to make it on-chip SRAM?